1. Field of the Invention
This invention relates to a magnetic head chip bonding device for bonding plural magnetic head chips to a base member. More particularly, it relates to positioning adjustment of respective magnetic head chips.
2. Background of the Invention
A composite magnetic head, including plural magnetic head chips T1, has an erasure magnetic head chip and a reproducing magnetic head chip or a recording magnetic head chip, bonded with an adhesive 60 to a common base member B1, as shown in FIGS. 1 and 2.
In order to secure the magnetic head chips to the base member in this manner, it becomes necessary to effect positioning adjustment of the gap-to-gap distance, parallelism, track positions or the like to high accuracy for each of the magnetic head chips.
Such setting or adjustment is performed in the following manner, as shown in FIGS. 3 and 4
(i) Referring to FIG. 3, a distance X between a magnetic gap g1 of a magnetic head chip T1 and the lateral surface of the base member B1 is adjusted. The direction of this adjustment is hereinafter referred to as an X-axis direction. At this time, a distance c between the magnetic gaps g1 of the respective magnetic head chips T1 is adjusted, as shown in FIG. 4. PA0 ii) Referring to FIG. 3, a distance Y between the magnetic gap g1 of the magnetic head gap T1 and the rear surface of the base member B1 is adjusted. The direction of this adjustment is hereinafter referred to as a Y-axis direction. At this time, an offset e in protrusion along the Y-axis of the magnetic head chips T1 is adjusted, as shown in FIG. 3, for aligning the protrusion of the respective magnetic head chips T1. PA0 (iii) Referring to FIG. 4, a distance Z between track edges E of the magnetic head chips T1 and the upper surface of the base member B1 is adjusted. The direction of this adjustment is referred to hereinafter as a Z-axis direction. At this time, an offset d between the track edges e along the Z-axis of the respective magnetic head chips T1 is adjusted, as shown in FIG. 4, for aligning the track edges E of the respective magnetic head chips T1. PA0 (iv) Referring to FIG. 4, a tilt g of the gaps g1 of the magnetic head chips T1 is adjusted. This adjustment is referred to hereinafter as azimuth adjustment. PA0 (v) Referring to FIG. 3, rotation .theta. of the magnetic head chips T1 on the upper surface of the base B1 about the Z-axis direction as an axis of rotation is adjusted. The direction of this rotation is hereinafter referred to as a .theta.-direction.
When bonding the plural magnetic head chips to the base member by such adjustment, the following method has so far been used.
The first method is to employ a pair of holding tools 61, such as electromagnetic collets, for positioning the magnetic head chips T1, which are bonded in the floating state without being contacted with the base member B1.
With this first bonding method, an UV curable adhesive 62 is applied to pre-set points on the base member B1 to which the magnetic head chips T1 are to be bonded. The upper surfaces of the magnetic head chips T1 are brought into contact with the holding tools 61, such as the above-mentioned electromagnetic collets, and thereby held magnetically. The holding tools 61 are moved along the X-axis, Y-axis, Z-axis and the .theta.-axis for shifting the magnetic head chips T1 to pre-set positions on the base member B1. At this time, the magnetic head chips T1 are placed over the base member B1 via the adhesive 62, such that the magnetic head chips T1 are not contacted with the base member B1, as shown in FIG. 6. In this state, UV rays are radiated for curing the adhesive 62. After the adhesive 62 is cured, the holding tools 61 are separated away from the magnetic head chips T1 to complete the bonding of the magnetic head chips T1.
However, since the contact area between the holding tools 61 and the magnetic head chips T1 is small, it is difficult to support the magnetic head chips in parallel with one another, such that sufficient azimuth adjustment cannot be achieved and azimuth defects tend to be incurred. On the other hand, it is difficult to apply the adhesive 62 uniformly such that differences in thickness are produced and the adhesive tends to be contracted in variable amounts at the time of curing of the adhesive 62. The result is offset in step difference adjustment and defects in track height. In addition, the holding tools 61 need to be secured until the adhesive 62 is cured to some extent, so that productivity cannot be improved.
The second method consists in gripping the lateral surfaces of the magnetic head chips T1 with a pair of holding tools 63 formed of a magnetic alloy for supporting and positioning the magnetic head chips T1 under the magnetism of the holding tools 63 as shown in FIG. 7. The magnetic head chips T1 are retained by a pair of magnetic head retention units 64 for provisionally holding the magnetic head chips T1 on the base member B1. The magnetic head chips T1 are subsequently bonded to the base member B1.
In carrying out the second method, a pair of the holding tools 63 formed of magnetic alloy are used to grip the lateral sides of the magnetic head chips T1 for supporting the magnetic head chips T1 using the magnetism produced by the holding tools 63. The magnetic holding tools 63 are moved along the X-axis, Y-axis, Z-axis and along the .theta.-axis for shifting the magnetic head chips T1 to pre-set positions on the base member B1. After completion of the positioning, magnetic head chip retention units 64 are applied against the upper surfaces of the magnetic head chips T1 under pressure for holding the magnetic head chips T1 against the base member B1. With the magnetic head chips T1 temporally held on the base B1 by the magnetic head chip retention units 64, the holding tools are detached from the magnetic head chips T1. An instantaneous adhesive is applied on and around the magnetic head chips T1 for securing the magnetic head chips T1. After curing of the instantaneous adhesive, the magnetic head chip retention units 64 are detached and moved away from the magnetic head chips T1 to complete the bonding of the magnetic head chips.
With the present second method, since the holding tools 63 and the magnetic head chips T1 are held in contact with each other by magnetism only, the magnetic head chips T1 are unstable in attitude and cannot be positioned accurately. In addition, when the holding tools 63 are removed from the magnetic head chips T1 after completion of positioning of the magnetic head chips, the magnetic head chips T1 are retained solely by the magnetic head chip retention units 64. Thus the magnetic head chips T1 tend to shift when the holding tools 63 are separated (disconnected) from the magnetic head chips T1. In addition, since the magnetic head chip retention units 64 contact the magnetic head chips T1 when separating the holding tools 63 away from the magnetic head chip retention units 64 after the end of positioning of the magnetic head chips T1, the magnetic head chips T1 tend to be shifted by contact with the magnetic head chip retention units 64.
The third bonding method consists in temporally retaining the magnetic head chips T1 set on the base member B1 using magnetic head chip retention units 65 and finely adjusting the positions of the magnetic head chips T1 manually. The magnetic head chips are bonded in the thus adjusted positions, as shown in FIG. 7.
First, the operator sets the magnetic head chips T1 as with pincers on the base member B1 and presses the magnetic head chip retention units 65 against the upper surfaces of the magnetic head chips T1 for provisionally holding the magnetic head chips T1. The operator then manipulates metal rods 66 (see FIG. 8) having pointed ends with both hands and, holding both sides of the magnetic head chips T1 therewith, shifts the magnetic head tips T1 to a pre-set position. After completion of positioning of the magnetic head chips T1, the operator applies the instantaneous adhesive to and around the magnetic head chips T1 for securing the magnetic head chips. After curing the instantaneous adhesive, the operator releases the magnetic head chip retention units 65 from the magnetic head chips T1 to complete the bonding of the magnetic head chips T1.
This method requires skill on the part of the operator since the magnetic head chips T1 need to be moved manually in the order of only several microns.
With the conventional method for bonding the magnetic head chips, it is difficult to achieve correct positioning and adjustment, thus producing defects in track height or azimuth, while skill on the part of the operator is required.